A slap in the face means an insult, rejection, or painful disappointment. The correct answer is this meaning because the expression is used figuratively, not only by its literal words.

Examples:

• The unfair mark felt like a slap in the face.
• In an HSC essay, A slap in the face can express this meaning: an insult, rejection, or painful disappointment.
• When this expression appears in a passage, connect A slap in the face with the idea of an insult, rejection, or painful disappointment.